Three-dimensional semiconductor mounting has become essential for higher density and larger capacity. A three-dimensional mounting technique is a semiconductor production technique for thinning a semiconductor chip, and connecting the chip to another chip using a through silicon via (TSV) to form a multilayer. In order to realize this technique, steps of grinding a non-circuit-forming surface (also referred to as “back surface”) of a substrate on which a semiconductor circuit has been formed to thin the substrate, and then forming an electrode including a TSV on the back surface, are required. Conventionally, in the step of grinding the back surface of a silicon substrate, a protective tape for the back surface is attached to a surface opposite to a surface to be ground for preventing breakage of the wafer during grinding. However, this tape uses an organic resin film as the base material, which has flexibility, but inadequate strength and heat resistance. Therefore, this tape is not suited to the steps of forming a TSV and forming a wiring layer on the back surface.
For this reason, a system has been proposed in which a semiconductor substrate is bonded to a support made of silicon, glass, or the like, through an adhesive layer to sufficiently withstand the steps of grinding a back surface and forming a TSV and an electrode on the back surface. In this system, the adhesive layer used for bonding the substrate to the support is important. The adhesive layer requires sufficient durability to bond the substrate to the support without gaps and to withstand subsequent steps. Further, it is necessary that a thin wafer can be easily delaminated from the support finally. Hence, the adhesive layer is finally delaminated, it is referred herein to as “temporary adhesive layer” (or, temporary adhesive material layer).
As to the conventionally known temporary adhesive layers and a method for delaminating the same, there have been proposed a technique in which high intensity light is irradiated to an adhesive material containing a light-absorbing substance to decompose the adhesive material layer whereby the adhesive material layer is delaminated from the support (Patent Literature 1), and a technique in which a heat fusible hydrocarbon compound is used for an adhesive material, and bonding and delamination are carried out in a heat-molten state (Patent Literature 2). The former technique has involved the problems that it requires an expensive tool such as laser, and a treatment time per one substrate is longer. The latter technique is simple because of control only by heat, but the applicable range is limited since thermal stability at high temperatures exceeding 200° C. is insufficient. Further, these temporary adhesive layers are not adequate to form a film with uniform thickness on a heavily stepped substrate and to provide a complete adhesion to the support.
Besides, it has been proposed to use a silicone adhesive agent for the temporary adhesive material layer (Patent Literature 3). This is to bond a substrate to a support by using an addition curable type silicone adhesive agent, and on delamination, the assembly is immersed in a chemical solution capable of dissolving or decomposing the silicone resin, whereby the substrate is separated from the support. Thus, this method takes a very long time for delamination and is difficultly applicable to the actual manufacturing process.
In view of the above-mentioned problems, there has been proposed a technique which uses a thermoplastic organopolysiloxane temporary adhesive layer and a thermosetting modified siloxane polymer temporary adhesive layer (Patent Literature 4). In this method, a temporary adhesive layer having some thermal process resistance can be formed with uniform film thickness on a heavily stepped substrate, and therefore it is highly compatible with steps of forming a TSV and forming a wiring on the back surface of the wafer, and delamination can be readily carried out. However, there is a problem of heat resistance at a high temperature exceeding 300° C.